As amazingfate (the Armbian dev for this device) clearly stated on the forum: cellular and camera are not working, only display, touch, wifi, and bluetooth are functional—so it won't replace your phone OS for calls and texts
that’s a super specific and annoying issue! It sounds like Armbian is still exposing an A2DP (audio) profile even after you tweaked the main.conf. Have you tried disabling the audio sink entirely via Bluetooth CLI or modifying the /etc/bluetooth/audio.conf (if it exists) to set AutoConnect=false under [General]?